Update yaws formula with v1.96 plus --HEAD option

Changes include:
* Update release from 1.94 to 1.96 in yaws formula using GitHub's releases URL
* Update `sha1` for new source archive
* Provide `--HEAD` option for yaws formula (needed for newer Erlang versions)
* Add `test` method with a basic tests for yaws formula
* Revert private method extraction to address method extraction from @adamv
* Use autoconf for yaws formula and specify build dependency on autoconf
* Add patches for yaws formula which is necessary for Erlang R16B01 and above
* Make tests valid for `--HEAD` builds even when the next version is bumped